Seoul Virus — A Rat Double-Cross

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Many New Yorkers might not believe it, but rats can make good pets. Not the typical rats we're familiar with in the subway, or those seen skittering around garbage cans after dark. No, we're thinking of domesticated rats — raised for generations to be friendly to people — they can have much to offer as pets. According to some vets, rats are clean, affectionate, and empathetic (!). Unfortunately, one item not in the plus column is a virus that can be harbored by pet rats and passed along to human handlers. This is the Seoul virus, a member of the hantavirus family, and according to a recent report from the CDC, there have been human cases of this virus in both the US and Canada traced to pet rats or rat breeding facilities.

In late 2016, a hospitalized patient in Wisconsin who operated a rat breeding facility, had fever, low white blood cell counts, high liver enzymes, and protein in the urine. And about a month later a family member of the patient also developed these symptoms. Testing revealed that the Seoul virus was the cause of their illness, likely from the rats in their facility. Since that time, the CDC identified 31 facilities in 11 states that had either human or rat virus infections.  But the outbreaks weren't limited to the US. Six of the breeding facilities had exchanged animals with Canadian facilities, and some Canadians were also identified as having anti-Seoul virus antibodies, indicating that they had been exposed.

Symptoms of a Seoul virus illness include fever (>101o), myalgia, headache, renal failure, conjunctival redness, thrombocytopenia, or proteinuria. All the patients identified in Canada and the US had the same virus strain, indicating common sources of the virus.

Although the reported cases didn't result in the most severe problems (e.g. kidney failure), that doesn't mean they couldn't occur, especially in persons with compromised immune systems. Thus the CDC warns that "all persons with rodent contact should avoid bites or scratches and practice good hand hygiene, especially children and persons with compromised immune systems. CDC recommends hand washing after caring for rodents and before eating, drinking, or preparing food." Further, they encourage all operators of breeding facilities to quarantine any new rats for 4 weeks and to test them for the Seoul virus before allowing them to interact with animals already in those facilities.

While the risk of a Seoul virus-illness may be low, it's important to check with sources of pet rats to be sure their animals are "clean" before purchasing them, and to follow good hygiene practices. Pet rats should be sources of pleasure for their owners — not of illness.